1. Field of the Invention
The present invention relates to the technical field of wheelchairs, especially for persons who are handicapped or elderly, or suffering from a disease.
2. Description of Related Art
The present invention relates to the technical field of wheelchairs, especially for persons who are handicapped or elderly, or suffering from a disease.
It is common knowledge that aside from a certain, very limited, improvement in comfort, and new elements such as electrical motorization, wheelchairs have not changed much from a technological perspective. To date, the best of them are constituted by a cycle part and a seat part, the cycle part being rudimentary in its design. In the prior art, the two parts are still considered globally by manufacturers, which partially explains the serious defects and disadvantages that remain. At best, overall changes have been made without providing any drastic improvement in a particular area.
The chief serious defects or disadvantages that still characterize the prior art after decades are:
vibrations on any rough or frequently uneven surface such as black top, gravel, cobblestone, the paving stones of pedestrian walkways, indoor or outdoor stone or tile, and the like, which are difficult, even painful for users;
the difficulty of negotiating obstacles such as sidewalks, steps, and the like, when ascending or descending;
the lack of shock absorption of any kind,
the risk of overturning in case of banked curves;
the seat of the chair, which is very poorly adapted, or non-adaptable, to the particular situation and hence to the comfort of the person in question; there is no real support of the individual, which in addition to mere discomfort, creates a risk of the person""s slipping and falling.
At present, two main types of wheelchairs are known.
There is a standard collapsible wheelchair, which is subject to Social Security reimbursement, and with which hospitals, homes for the elderly, various centers involved with the problems of the handicapped, and certain service organizations are equipped. The assistance of a third person is required for its use, particularly for negotiating obstacles; this chair is heavy and difficult to handle, and storing it has proven to be complicated.
There is also a lightweight chair that can be considered to be a xe2x80x9csportxe2x80x9d chair, collapsible or non-collapsible, better looking and easier to handle, which is aimed at a clientele of independent users who seek greater autonomy and/or have to perform exercises.
Many changes have appeared for making these chairs more adaptable between ordinary and xe2x80x9cindependentxe2x80x9d or xe2x80x9csportxe2x80x9d use, but the defects mentioned above have not been eliminated. This is especially true for the kinematic part, the suspension, the flexibility of the wheel trains, the filtering of vibrations. The prior art has been limited to providing a change in the camber of the wheels (i.e., the angle of the plane of the wheel relative to the vertical), making it possible to switch from indoor use (taking up a minimum of space, in order to pass through standard 80-cm wide doors) to outdoor or xe2x80x9csportxe2x80x9d use (camber adjusted for better stability). However, handling remains complicated and no solution is provided with regard to vibrations or the negotiation of obstacles. A slightly lower risk of overturning is obtained, but only at the cost of an adjustment that is difficult for the user to perform.
To give a structural example, all of the current non-collapsible wheelchairs comprise a single rigid crossbar that supports the wheels of large diameter, and all the chairs are based on this immutable concept.
As for the current small front wheels, one skilled in the art knows that it is not unusual to see out-of-round wear on the joint, which can result in the breakage of the piece, caused by the mechanical stresses sustained by the fork, which stresses are even greater when they act on wheels of small diameter.
There is the known patent EP 0 384 499, according to which the central suspension comprises a funicular quadrilateral with an articulated parallelogram in order to reduce the risk of overturning backward during an effort. This document does not solve the same problem as the present invention, and its technical solution is unrelated. However, this document clearly illustrates the multitude of problems, discomforts and even risks that the user must face.
It seems that the profession is satisfied with this state of things, the vast majority of clients by definition not having much control over their choice, while cost considerations, which are important, have prevailed against any major innovation.
Also known through the document U.S. Pat. No. 5,180,025, which may be considered to describe the closest prior art, is an electric wheelchair in which the wheels are mounted on a rudimentary suspension system. The latter is constituted by two helical springs, each pivotably joined to the frame of the chair by one end, and to a wheel support arm by the other end, said arm itself being joined by a pivot joint to a fixed piece of the frame.
Also known through the document U.S. Pat. No. 2,126,084 is a suspension system for motorized vehicles. It is an old document (1933), specifically devoted to suspensions for automobiles, and does not apply directly to wheelchairs. The main object pursued in this document is to provide a suspension system comprising a suspension for each wheel independent of the other wheels, housed in a tubular part of the body of the vehicle, which can be removed in one piece with the rest of the axle.
The value of the invention is that it approaches the problem from another angle, i.e., globally, and presents an overall technical solution that simultaneously eliminates a number of drawbacks.
The invention also provides many heretofore unknown advantages.
According to an essential concept of the invention, a chassis with a rigid center beam is used. Another essential concept of the invention resides in a rear suspension with a high clearance. For this reason, the rear suspension (AR) comprises an upper articulated triangle, a lower strut forming a countershaft to a shock absorber, with a wheel support pin.
The central beam can have any cross section, for example square or rectangular, depending on the cost. It would be preferable, however, for the beam to have an inverted trapezoidal cross section (small base at the bottom) in order to facilitate the collapsibility of the chair as described below, and to generate a negative cambering, also as described below.
Collapsibility is facilitated by a beam with an inverted trapezoidal cross section in that, by releasing a locking means that will not be described herein, the entire structure is lowered by gravity with a deformation of its geometry, the folding of the parts being facilitated by the trapezoidal shape, with suitable indentations cut into the edge of the beam in order to allow a complete folding.
Furthermore, a beam with an inverted trapezoidal cross section makes the triangle (1) (FIG. 3 and description below) shorter than the lower strut (6a). Thus, during compression, for example during a turn, the lowering of the beam (vertical force represented by the arrow) translates (arrows) into a negative cambering of the wheel (i.e., the top part of the wheel is displaced inward); this results in better stability on the ground and hence better road-holding.
An adjustable shock absorber/telescopic spring is attached to the countershafts of the lower struts, and is mounted transversely inside the chassis beam. A helical shock absorber that allows a high clearance, or any other system allowing a high clearance, is entirely preferred.
The small front wheels (AV) are mounted on fixed or articulated struts with an original vibration filtering system, which is mounted on the support plate.
It must be noted that, in an entirely preferred way, the assembly of the parts of the suspensions AR and AV is mounted directly on the beam.
This assembly provides a level of comfort such that it becomes possible to consider, for the seating, a seat and a back made of foam or any similar material, preferably molded or otherwise adapted to the morphology of the particular subject. Without this assembly, a comfort and support system such as a molded seat would lose most of its advantage. There is therefore a synergy between the technical innovations of the rolling chassis and the rigid molded seat, the overall result being an exceptional level of comfort obtained for the first time.
The rigid molded seat is an important element of the invention because it allows a complete adaptation to the morphology of the subject, and therefore prevents any dangerous effects such as the lateral shifting or forward sliding of the subject, while avoiding the disadvantages of a poor seating position.
The word xe2x80x9ccomfortxe2x80x9d in this case means not only the comfort of the seating, but also the comfort of the rolling, support, suspension, negotiation of obstacles, the substantial reduction in the rolling vibrations, better handling, improved safety, etc.
The novel chassis also makes it possible to mount wheels with harder and stronger treads; in fact, in the conventional chairs, the shock-absorbing function is devolved to the wheels. They are therefore equipped with treads that are as flexible as possible, but have two serious drawbacks for a handicapped person: first, a flexible tread creates greater resistance to forward motion, which requires a substantial muscular effort, and secondly, a flexible tread of this type is subject to punctures.
The invention has opted for the opposite principle, which is to provide comfort through the chassis, and thus to be able to use treads that are hard, hence having little resistance to forward motion through friction on the ground, and no risk of puncture.
The vibrations due to rough surfaces are absorbed as a result of doubly triangulated load-bearing suspensions; the potential deformation of the trains makes it easier to negotiate obstacles, smoothly and with less effort; the original suspension allows better course-holding and road-holding than that of the current models, since this suspension absorbs stresses and maintains the xe2x80x9ccamberingxe2x80x9d of the wheels, with a correction of the angular position of the chair during banked curves. The risk of lateral overturning is therefore greatly diminished without the user""s ever having to manually change the adjustment of the camber, which is both difficult and often physically impossible (requiring leaving the chair). Finally, the original design makes the chair easy to handle, while also taking up less space.